If we could, should we?

[Mr. 16 gauge]

I watched a rerun of "Jurrasic Park" a few weeks back, and while crow hunting last week got to thinking about another movie re: cloning, i.e. "The Boys from Brazil", and then I got to thinking.....what if we could bring back extinct species via DNA manipulation?
While I don't think that anyone wants to bring back Adolf Hitler (there are enough Hitler-esque types around as it is) or a T-Rex (or worse, a T-Rex/Hitler hybrid!), what about species that have become extinct directly as a result of man's involvement. I'm thinking of species such as the passenger pigeon, Labrador duck, and heath hen. There may be other species out there (black footed ferret?) that might be included.
We've seen the negative effects of bringing back species from the brink of extinction....look at what the wolves have been doing to the elk populations around Yellowstone and upper Michigan, or the protection of alligators. But then again, man's involvement (i.e. no plan as to what to do if the species gets out of control/too populated) has more to do with it than anything.

Could there be some possible benefit to bringing back such species, something like possibly filling a niche that has been taken over by an invasive species? I don't know for sure, but it is possible.

I'm sure that there are ways to get such DNA, such as feathers/study skins that are sitting in collections in areas such as the Smithsonian.

So....what do you think? Should we try and bring back species that went extinct directly due to man's involvement (not natural causes), or leave well enough alone.

I look forward to your comments.